textproduct: Quad Cities

KEY MESSAGES

- Chances for showers/storms return this evening and overnight as a weak cold front arrives in the area.

- High pressure will bring a period of much needed quiet and dry weather Sunday through Monday, prior to the pattern becoming more active Tuesday through midweek.

- Strong to severe storms are possible Tuesday, as a much more potent cold front arrives into the region.

SHORT TERM /THROUGH TONIGHT/

Issued at 113 PM CDT Sat Aug 15 2026

Low level moisture remains plentiful over the region in the wake of the overnight storms and heavy rain. These rains fell in the southern 1/2 of the area, and were heaviest in our far southern counties. We now have saturated conditions found south of I-80, and rather wet soil conditions found to the north. This antecedent condition will keep the threat for isolated flash flooding possible for any slow moving or strong thunderstorm tonight.

We do have the treat for additional storms tonight, but with a much smaller footprint of heavy rainfall expected, and reasonable confidence it will be a narrow swath of heavy rain, I am inclined to hold off on any new flood watch for now.

Looking at the environment, much like yesterday, nearly every model is too warm regarding low level temperatures, but humidity remains very high, and is handled reasonably well. Thus, far, this combination is keeping heat index readings under 95 degrees in all areas. Tonight, the front will arrive rather late at night, if not nearly morning, however, a pre-frontal wind shift to the west is expected to combine with lift from a mid level short wave to bring showers and storms to the area. There is quite a bit of variation in placement of storms tonight, but decent agreement on timing and character of storms. A small cluster, possibly with an advancing cold pool is forecast to move through between 7PM and Midnight. PWATs remain very high, around 2 inches, but movement should be rather quick, especially if storms are strong. Thus a narrow stripe of QPF around 1 inch is possible, with amounts elsewhere very low, or dry. SPC generally is following that progression as well, as we remain in a marginal, level 1 risk. The late evening arrival supports a cold pool and faster movement as well, in a mature stage of convection. Wind gusts of 40-50 mph can be expected with this line, with some threat 20-30% for winds over 60 mph.

LONG TERM /SUNDAY THROUGH SATURDAY/

Issued at 113 PM CDT Sat Aug 15 2026

Sunday Through Monday...

This timeframe will be relatively quiet, as we will be fully post frontal and generally in cool/dry advection by midday Sunday. Upper wave and cold front will be east of the area by early Sunday morning, which will effectively help flatten the ridge that was set up over the area the last week, which brought persistent rainfall. Thus, this will shunt the active baroclinic zone south of the area, with surface high pressure passing over through Monday. A period of quiet and dry weather will be seen, with near seasonal temperatures. Monday looks to be a beautiful day with mostly clear skies. Enjoy this reprieve from the active stretch of weather that the region has been experiencing, as the pattern becomes active once again Monday night through midweek.

Tuesday and Beyond...

Monday night into Tuesday, weak ridging will pass east of the area, pushing the surface high pressure out and resulting in increasing llvl southwesterly flow. Temperatures and moisture will both increase on Tuesday, with best moisture moving in later in the day. LLJ will kick in Tuesday evening and through the night, as a quick- moving upper wave approaches the area from the northwest. A seasonally strong cold front will accompany this wave, providing sufficient surface and upper level forcing for thunderstorms. A brief look at model soundings during this timeframe would indicate the potential for an overnight complex of thunderstorms passing through the area, as we have seen over the last week. The main difference with this system is that it will be progressive, pushing out of the area by early-midday Wednesday and leaving us in a post- frontal airmass through the remainder of the week. The best moisture will move into the area ahead of the cold front Tuesday night, with global guidance indicating 1.50-2.00" PWATs moving in. Thus, heavy rainfall will be on the table with these storms. It is still early, but SPC is outlining that period for a Slight, level 2, severe threat, given the pattern and environment in place.

After this wave pushes out of the area on Wednesday, we will see weak zonal-northwesterly flow set up again over the region. Surface high pressure will pass through late in the week, which should bring a period of mostly dry weather. Although, there remains some uncertainty, as some long term models indicate subtle waves passing through bringing low-end PoPs. NBM favors the mostly-dry forecast, leaving PoPs <20% through Friday. The post-frontal airmass will keep temperatures cooler through the second half of the week, with most in the mid 70s.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 632 PM CDT Sat Aug 15 2026

A weak cold front will move through eastern Iowa and northwest Illinois this evening and tonight, bringing a chance for scattered showers (20-50%) and storms mainly south of CID. With low confidence on areal coverage, have mentioned the thunder chances at MLI and BRL in PROB30s. Occasional MVFR ceilings are possible at MLI overnight into Sunday AM, with periods of IFR likely at DBQ. Additionally, fog may develop at DBQ tonight with potential for visibilities to drop near or below 1 mile at times.

HYDROLOGY

Issued at 1225 PM CDT Sat Aug 15 2026

Rainfall ranging from 2 to 6 inches,fell across southern parts of the area, mainly south of the tributary forecasts it was expected to fall 24 hours ago. This is a helpful thing, though flooding did impact portions of McDonough through Lee County overnight, and this warranted minor flood warnings for the Skunk River at August today, and a moderate flood warning for Colmar, on the La Moine River.

Flood warnings and watches on portions of the Iowa, Wapsipinicon, and upstream Skunk have been cancelled, as this rainfall fell south or downstream of these forecast points.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.